Hey there!
I had to face the same question aswell when I upgraded my old cheap MtB into something new with hydros. - I disassembled the brake lever from the gear body (which you can do) and then shoved the new hydro brakes next to it. - I found that it was awkward for me to hold the brakes + the triggers for the shifters at the same time, but I rarely hold both at the same time.
Hindsight, I'd of loved to try out Cable Actuated Hydraulic Disc Calipers firstly instead. - Try googling them, see if it takes your fancy.